how do you change an airline's culture and how long does it take
20 years minimum at least I would say based on my exeprience in a multinational environment .(not airline but very close)
A very surprising ( for me it was at least) feature about culture : you see older generation passing it on to younger ones who were reluctant at first, but when 15 years later those young guys are replacing the old ones,they keep applying the old culture and teach it to the younger ones below them.
In the case of AF, the problem is complicated because you have to add a internal very powerful Union plus a long tradition and culture of doing things differently.
How to do it ? ask companies who managed it successfully recently : Emirates, Etithad, Qatar, Bristow helicopters, etc.. It is painful and not very democratic.